5 Quantities and units library [quantities]

5.4 Reference [qty.ref]

5.4.4 Unit [qty.unit]

5.4.4.5 Types [qty.unit.types]

5.4.4.5.4 Prefixed [qty.prefixed.unit]

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namespace mp_units { template<symbol_text Symbol, UnitMagnitude auto M, PrefixableUnit auto U> requires(!Symbol.empty()) struct prefixed_unit : decltype(M * U)::base-type { using base-type = prefixed_unit; // exposition only static constexpr auto symbol = Symbol + U.symbol; // exposition only }; }
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prefixed_unit<Symbol, M, U> represents the unit U with a unit prefix (IEC 60050, 112-01-26).
Symbol is the symbol of the unit prefix.
M is the factor of the unit prefix.
A specialization of prefixed_unit is used as a base type when defining a unit prefix.
[Example 1: template<PrefixableUnit auto U> struct kilo_ : prefixed_unit<"k", mag_power<10, 3>, U> {}; template<PrefixableUnit auto U> constexpr kilo_<U> kilo; inline constexpr auto kilogram = kilo<si::gram>; — end example]